Ryanair boss Michael O'Leary has warned that the budget airline will be forced to scale back British investment if the country votes to leave the European Union.

Appearing on a platform with Chancellor George Osborne at Stansted Airport, Mr O'Leary said that inward investment will be lost to competitor EU member states such as Ireland and Germany if Britain votes for Brexit.

He also announced the creation of 450 new jobs in Britain as part of a 1.4 billion US dollars (£976 million) investment into the Ryanair's 13 UK bases.

Mr O'Leary said: "It is this type of large-scale foreign inward investment that is helping to drive the UK economy and job creation.

"It is exactly this type of investment that will be lost to other competitor EU members if the UK votes to leave the European Union."

The outspoken Irishman also urged the British public to vote to Remain on June 23.

He said: "The single market has enabled Ryanair to lead the low-fare air travel revolution in Europe, as we bring millions of British citizens to Europe each year, and welcome millions of European visitors to Britain, and we are calling on everyone to turn out in large numbers and vote Remain," he said.

Mr O'Leary was speaking at the opening of Ryanair's European Training Centre at Stansted, which will create more than 1,000 new jobs overall for pilots, cabin crew and engineers this year.

Charlie Cornish, chief executive of Stansted owner Manchester Airports Group (MAG), said leaving the EU would be a "huge backward step for UK aviation".

The announcement comes after more than 300 business leaders urged Britain to vote to leave the European Union, warning that the country's competitiveness is being undermined by its membership.

In a letter to The Daily Telegraph, they argued that businesses will be "free to grow faster, expand into new markets and create more jobs" if they are unconstrained by EU rules.

Signatories include Peter Goldstein, a founder of Superdrug; Steve Dowdle, a former vice-president Europe of Sony; David Sismey, a managing director of Goldman Sachs, and Sir Patrick Sheehy, the former chairman of British American Tobacco.

Mr O'Leary, speaking in front of a Ryanair Boeing 737 emblazoned with the slogan "stronger, safer and better off in Europe" warned that Brexit would see air fares rise.

He said: "If Britain leaves the single market, Britain may be forced out of the open skies regime and air fares and the cost of holidays will rise.